i.MX8MQ PCIe1 Gen2 doesn't scan properly sometimes

[pengcheng]

Hi,

This is my hardware connection:

i.MX8MQ PCIe1 M.2 slot <---> M.2 convert to miniPCIe <---> PCIe bridge <---> PCIe netcards intel 82574 L

Linux version is:

Linux version 4.9.51-imx_4.9.51_imx8m_ga+g6df7474 working at PCIe1 Gen2

Power up the board, sometimes PCIe1 controller doesn't scan properly, and can't find the PCIe card.

And sometimes, this happens with high probability.

If I remove the PCIe bridge, PCIe card will work properly.

But when it doesn't scan properly, the GEN2 link is still up, so are there any registers I can check?

->imx6q-pcie 33c00000.pcie: Link up, Gen2

Please give me some hint. Thanks!

BR,

Peng

[igorpadykov]

Hi Peng

issue may be caused by weak signal due to losses in connectors,

also one can check PCIe voltage rails if they are clean and without ripples.

May be recommended to test with latest linux L4.14.78:
linux-imx - i.MX Linux kernel 

Best regards
igor
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[pengcheng]

Hi irgor,

Thanks for your quick reply, I had done some tests.

1.issue may be caused by weak signal due to losses in connectors

I used imx6 sabresd to compare, it also use the PCIe bridge, but it always scan successfully.

So we can see maybe that is not the problem.

2.May be recommended to test with latest linux L4.14.7

I used the newest version, it has the same issue.

3. About what I said last time "If I remove the PCIe bridge, PCIe card will work properly."

It is wrong, when I use PCIe card directly, it works on Gen1, so can not compare this to bridge circumstance.

My question is whether NXP has the test result for PCIe1 Gen2 with Linux? Or are there anything I was missing?

BR,

Peng

[pengcheng]

Hi igor,

I see this file, there is no PCIe Unit test. I want to know, does NXP test PCIe1 GEN2 in i.MX8MQ-evk board?

<i.MX Reference Manual Document Number: IMXLXRM Rev. L4.9.51_imx8mq-ga, 03/2018>

BR,

Peng